This invention relates generally to a replaceable cutting bit holder assembly and particularly to an assembly having a fixed base member to which a removable tool holding block is attached.
For many years the conventional method of attaching cutting bits to the cutters of continuous mining machinery was to provide bit holding blocks which are directly welded to the mining machine cutters. Consequently, replacement of such tool holders required the use of a cutting torch handled by an experienced welder. Because of the difficulties in finding suitably qualified welders, and because of the problems encountered in welding in the face area of a coal mine such blocks, and therefore the associated bits, were simply not replaced and the machines were operated with a decreased number of bits. The result of this was that adjacent bits became overloaded and the remaining bits and blocks suffered progressively increasing wear, until such time as the entire cutter of the machine had to be replaced with a new cutter and the old one sent out for repair.
In those instances in which an attempt was made to replace the worn bit blocks by welding new ones in position, the attack angle of the bits was frequently out of alignment because of errors in positioning the blocks.
Because of the inadequacies of the above system, replaceable tool holders have been devised which provide a separate tool holding lug or block member removably attachable to a base member, the base member being fixedly attached to the mining machine cutter. An example of a replaceable tool holder is disclosed in U.S. re-issue Pat. No. 28,310. This holder consists essentially of a block member connected to a base member by means of a transverse pin. One of the two connected members is bifurcated to receive the other of said members and the transverse pin connects the two members together in double shear. In principle, the damaged member block is replaced by simply removing the pin connecting the block member to the base member. Unfortunately, because the base includes outstanding portions, such portions also tend to become damaged with the result that proper repair of the assembly in some instances requires replacement of the base members in addition to replacement of the bit-holding block members attached thereto.
The problems inherent in the tool holder assemblies discussed above have been solved by the present device in a manner which is neither disclosed nor suggested in the prior art.